body {
    margin: 0;
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'Roboto', 'Oxygen',
        'Ubuntu', 'Cantarell', 'Fira Sans', 'Droid Sans', 'Helvetica Neue',
        sans-serif;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

code {
    font-family: source-code-pro, Menlo, Monaco, Consolas, 'Courier New',
        monospace;
}

.btn {
    background: none;
    border: 1px solid #000;
}

/* CSSTransition库样式 start */
.mydemo-enter,
.mydemo-appear {
    opacity: 0;
}

.mydemo-enter-active,
.mydemo-appear-active {
    opacity: 1;
    transition: opacity 1s ease-in;
}

.mydemo-enter-done {
    opacity: 1;
}

.mydemo-exit {
    opacity: 1;
}

.mydemo-exit-active {
    opacity: 0;
    transition: opacity 1s ease-in;
}

.mydemo-exit-done {
    opacity: 0;
}

/* CSSTransition库样式 end */